Mutagenesis by ultraviolet radiation in bacterial cells will be investigated. Particular modes of reversion will be identified and studied extensively, to determine specific mutagenic processes. Specific mutagenic processes will be related to aspects of DNA repair by concomitant biochemical studies of DNA metabolism. These studies should identify fundamental processes by which cells cope with unusual molecular residues in their genetic material and survive withe occasional genetic alteration. BIBLIOGRAPHIC REFERENCE: Haak, R.A., and R.C. Bockrath (1975). "Pyrimidine dimer excision and mutation frequency decline." Rad. Res. 61, 164.